During presentations, use of a projector to project an image onto a projection screen so that the image can be seen by attendees is common. In many instances, presenters interact with the displayed images using a pointer to highlight and emphasize displayed information. During such interactions, presenters must often move between the projector and the projection screen and into the projected image. If the presenter moves into such a position and turns to face the audience, the projected light can be blinding. Subjecting a presenter's eyes to light of this nature is of course undesired.
Techniques to avoid exposing a presenter's eyes to projected light have been considered. For example, U.S. Pat. No. 6,361,173 to Vlahos et al. discloses a method and apparatus for inhibiting projection of selected areas of a projected image. The apparatus includes a video projector for projecting a desired video image onto a projection screen. An infrared source close to the video projector uniformly floods the projection screen with non-visible infrared radiation. An infrared sensitive camera, close to the video projector, observes the projection screen and sees only the uniform infrared illumination flooding the projection screen. Upon entry of a subject into the projected video image, the infrared radiation reflected from the subject will not match that of the projection screen and thus, the subject area can be identified. All pixels of the projected video image, in the area occupied by the subject, are inhibited before reaching the video projector. This allows the subject to look directly at an audience without being blinded by light projected by the video projector.
U.S. Pat. No. 6,860,604 to Vlahos discloses a method and apparatus for inhibiting the projection of a shadow of a presenter onto a projection screen. Left and right rectilinear corrections of an image are simultaneously projected onto the projection screen from each of two positions that are off-axis on opposite sides of the centerline of the projection screen such that both projections register as a single image. A center of mass of the presenter's silhouette is generated. A vertical join line is located on the projection screen directly behind the presenter's center of mass. The portion of the projected image from the left projector that extends to the right of the join line is inhibited. The portion of the projected image from the right projector that extends to the left of the join line is also inhibited thereby providing the full projected image on the projection screen from the left and right image segments, without either segment projecting the image onto the presenter and without casting the presenter's shadow onto the projection screen.
U.S. Pat. No. 6,945,653 to Kobori et al. discloses an anti-glare device for a projector designed to minimize stimulus to the eyes of a presenter. A displayed image captured by a camera is compared with an input image signal to generate a difference image and thus, detect the location of the presenter. The input image signal is then masked so that pixels corresponding to the area at which the presenter is located are set to black. The resulting projected image signal is then projected onto the projection screen.
Although the above-references disclose techniques to inhibit projected light from being directed into the eyes of a presenter, the systems disclosed in these references suffer disadvantages. For example, although the systems disclosed in U.S. Pat. No. 6,361,173 to Vlahos et al. and U.S. Pat. No. 6,860,604 to Vlahos avoid light projected by the projector from being directed into the eyes of a presenter, the systems still expose the presenter's eyes to infrared light. Also, each of the above-described systems determines a tight-mask defining the location of the presenter and thus, requires high-resolution cameras.
As will be appreciated, there exists a need for a projection system designed to protect a presenter's eyes from virtually any form of projected light, which is easy to manufacture and cost effective. It is therefore an object of the present invention to provide a novel method and apparatus for inhibiting a subject's eyes from being exposed to projected light when the subject is positioned in front of a background on which a projected image is displayed.